Gases which have been stored in containers such as cylinders or pipelines under immense pressure. The most commonly used at UMN are: 

• Nitrogen
• Propane
• Carbon Dioxide
• Hydrogen
• Nitrous Oxide
• Ammonia
• Chlorine
   

Compressed gas cylinders might contain only one type of compressed gas or a special blend with multiple types of gases.

Health Hazards

• Health hazards will vary from gas to gas. Consult the Safety Data Sheet (SDS) and cylinder label for the most accurate information.
• In addition to the health hazard of the gas itself, released gases will displace oxygen from an area, creating an asphyxiation hazard.
• Because of the pressure they are held at, gases are extremely cold when released quickly to atmospheric pressure. Frostbite to exposed skin or eyes can occur.

Physical Hazards

• Compressed gas cylinders are under extreme pressure; standard lab cylinders are generally over 2000PSI. Cylinders and especially their valves must be protected against damage and collision.
• To minimize risk of explosion during fire, kill or remove all vegetation and other combustible material from outdoor bulk storage of flammable gases (e.g., propane).

Safe Work Practices

• Work with compressed gas systems should use our Standard Operating Procedure Template for Compressed Gases.
• Systems where multiple lines are present with different gases must have lines labeled with either different colored lab tapes and an easily visible legend or legible writing of each gas for larger lines. Labels must be present after each change of direction and at each valve of hard-piped systems.
• Lines, valves, and connectors must be compatible with the gases inside of them.

  • Flammable gases, including Bunsen burners must use appropriate flammable gas tubing.
     

    

• Check for leakage of systems first with an inert gas or compressed air before running a hazardous gas through a system.
• Watch out for signs of leakage, such as odor, frost, hissing sounds, etc. (see Leak Testing section for additional methods)
• Always wear Personal Protective Equipment (PPE), including goggles and gloves (if required) when making/breaking compressed gas connections.
• Transfilling, or pressurizing and filling of your own compressed gas cylinders, is not to be performed without the expressed approval of and thorough safety and equipment review with your HSRM safety partner.

Leak Testing

Leak testing can be performed through a variety of means, including the soap solution bubble test for a low-accuracy visual check, or with specialized tools such as ultrasonic detectors.

• Soap solution bubble test: apply a soapy solution to the connection points on the pressurized system; bubbling will indicate a leak at that connection. Note that this method works for uncomplicated setups, but may have lower accuracy for complex systems and can be messy.
  • When performing the soap solution test, always
    wipe the area clean before reapplying in order
    to prevent false positives.
• Ultrasonic detectors: these are devices that detect high-frequency sounds, which are associated with compressed gas leaks. These work well, even in loud environments, and can be used to pinpoint a leak based on signal strength.
  • Always ensure that electronic leak detection equipment is calibrated, and follow the manufacturers instructions.
• After leak testing, depressurize the system before tightening the connections or fittings.

Storage

• 

  Store cylinders (empty or full) in designated areas. Protect from impact, sunlight, heating, corrosion, water damage, and very low temperature.

• Cylinders must be secured in an upright position using methods which provide adequate physical strength and  integrity.
• Upright cylinders must be secured with a durable strap or chain on the upper third of the cylinder to a wall or stable surface.
• Cylinders in bulk storage can be nested, but must have three points of contact with each other. See CGA P-1 Appendix A, Standard for Safe Handling of Compressed Gases in Containers for more information.
• Separate oxidizing and flammable gases by at least 20 feet or by a protective, fire rated barrier.
• Valve protection caps must be in place until the cylinder is secured and must be on unless the cylinder is in active use.

Transportation

• Never drag cylinders or roll them on edge to transport them. Always use a cart and secure the cylinder to it using chains or other sturdy means.
• Compressed gas cylinders are not to be transported on personal or UMN fleet vehicles off of campus property without HSRM approval and a plan for securement
  and proper transportation paperwork.

Disposal

• Once a cylinder is no longer needed or empty (~30PSI), contact your compressed gas supplier to request a cylinder swap or pick-up. If for any reason you cannot return the gas to the vendor, contact HSRM for disposal assistance.
• Even if a tank is marked as empty, it must still have the protective cap in place.
• If a cylinder is displaying signs of severe damage such as flaking rust, pitting, bulging, or you can no longer identify the type of gas in the cylinder, contact Health, Safety, and Risk Management at (612) 626-6002 for disposal advice.